Hello all, Trying to decide on the final pieces for my set up. I know I did it backwards but some deals came up before I could decide on speakers. I am down to a few choices for my speakers, but I do have one nagging question. The room that everything is being set up in is only 12' X 16' so speaker placement will probably be a big issue. My question is....will a front ported set of speakers allow me to place them closer to the back wall? I know some adjustments will be necessary and it will depend on the speaker characteristics. But in general will front ports make better sense? Thank You!
The audibility of coloration from a delayed signal gently peaks at about 2 milliseconds as I recall (based on an AES paper by by James M. Kates), corresponding to a path length difference of about 27 inches, but remember that the point of origin for the sound that emanates from the port is the back of the woofer cone, so that must be taken into account.
The significantly greater distance that must be travelled to reach the ears for the midrange output from a rear port in a nearfield setup (in comparison with the distance from a front port) means that it will probably be about 6 dB or so down in level compared to the output from a front port, and this will make a more significant difference than if the rear reflection distanace happens to correspond to 2 milliseconds. In addition, if the reflective surfaces around the rear port are not 100% reflective in the midrange, then that much less of its output will be reflected to the ears.
Uneven bass due to room modal behavior is generally worse in small rooms than in large ones, so the relative benefit from having the woofer and port interacting with the room modes differently (due to physical displacement in two or three dimensions) is theoretically greater in a small room.
Hence my position that well-though-out rear ports are likely to be superior in a nearfield or small-room setup.
In my opinion a nearfield or small-room setup would be where well thought-out rear porting is most likely to be superior to front porting, for reasons mentioned in my earlier post. -Audiokinesis
Not really, when in the nearfield the reflected rear port output delay is very noticeable and is an issue, better to be front firing when doing nearfield speakers.
Weseixas, I believe that the fundamental resonance of an open-on-both-ends tube will occur at the frequency where the tube's length is equal to one-half wavelenth. For a port 6" long, that would be about 1.1 kHz.
In my opinion a nearfield or small-room setup would be where well thought-out rear porting is most likely to be superior to front porting, for reasons mentioned in my earlier post.
"Finally, nearly all ports have a resonance in the midrange region (imagine talking through a cardboard tube), so all else being equal we'd like that unwanted midrange energy to start out facing away from us and to travel as long as path as possible before reaching the ears" -Audiokinesis
Bingo ... !!!
Is that 2nd or 3rd harmonic Duke?
Such a phenom is also present with large paper cone woofers playing into the midband region, such a speaker is very much favored in Horn systems, along with a front firing port system. This is very much what panel owners notice and label as "sounding boxy" when listening to monopole box speakers.
A rear firing port is best not used in a size restricted room and if listening nearfield then a front firing port system is superior. Ultimately if you have the space a rear firing port IMO is superior to the front firing for sonics..
"The position too near the wall, so to speak, usually manifests itself in nearfield reflections, a larger problem imho than port constriction." - Lrsky
Well said - I agree 100%.
Regarding port location, note that if the speakers are designed for placement near room boundaries, the location of the port relative to those boundaries has already been taken into account. Audio Note, for instance, designs their rear-ported speakers for corner placement. Best to examine the specifics of a given speaker design rather than make decisions based on "rules of thumb" that have notable exceptions.
Even if a rear-ported speaker wasn't designed for placement near the room boundaries, in many cases it's possible to lower the tuning frequency by lengthening the port and/or reducing its cross-sectional area. This causes the speaker's inherent bass output to start rolling off higher up but not as steeply, so that it synergizes better with the additional room gain. This can of course also be done with a front port also, but it's more likely to be visually unacceptable.
One acoustic argument in favor of a rear port is that in most cases, with a bit of toe-in, your two bass sources (woofer & port) are now a different distance from room boundaries in all three dimensions. Thus their outputs will interact with the room modes a bit differently, in some cases smoothing the in-room bass significantly as compared with an equivalent front-ported speaker.
Finally, nearly all ports have a resonance in the midrange region (imagine talking through a cardboard tube), so all else being equal we'd like that unwanted midrange energy to start out facing away from us and to travel as long as path as possible before reaching the ears.
The alternative to ported (front or rear) is acoustic suspension. "Sealed" is not necessarily true acoustic suspension, indeed these days it is hard to find a woofer with specs optimized for AS. If you plug the port you do not have AS.
Yes, front ported speakers will definitely make a difference in a smaller room.
As an example the Linn Majik 109 speakers (front ported) were originally designed for small Japanese appartments. A friend of mine has these inside a bookshelf (1-2" rear clearance) and they sound fantastic!
lots of room / speaker / amp interactions here, so I would be tempted to test and give a good listen. Do you plan tube or SS amplification? Can you live with full range single driver speakers? Some front ported TL speakers could answer your question.
The position too near the wall, so to speak, usually manifests itself in nearfield reflections, a larger problem imho than port constriction.
Port velocity is usually well controlled in better speakers, with damping material--which changes the pitch AND therefore velocity of the air escaping. So close proximity is usually more of a nearfield issue, in my experience.
Your electronics dictates some of this 2 , if running tubes for eg. in a small room you will want to stay away from ported full bandwidth speakers where the lack of bass control from the amplifier will make the speaker interact badly with the room.
Also, consider sealed designs, such as Merlin monitors. Prior to my current setup, I was using Tyler acoustic monitors that were front ported. They were very good, but I could never elimnate a degree of "bloom" in the lower frequencies in my 11 x 20 room. On a whim I plugged the ports and found that they integrated a lot better with my room. Based upon results of the experiment, I replaced the Tylers with the Merlin monitors, which are sealed, and they are excellent in my room. I've even added a pair of sealed subs with great success. YMMV.
A fair number of speakers are designed to be "near wall" compatible. The VSA VR-33 is a recent example. Front and rear (and bottom, I think) can be made to work. You might try searching here for "near wall," and also companies like North Creek and Guru who make speakers specifically designed for this application.
Personally, I'd find the moving speakers out for critical listening a PITA -- much of my listening is background punctuated by occasional "stop and listen" breaks. But as Schipio says, it's a way to go, if a "free field" speaker is best for you in other respects. You have to be OK with some tape on the floor, though; Meiwan is right that placement is a game of inches.
Yes, front porting gives you more flexibility in placement. Although some rear ported speakers can work OK close to a wall (ie, Linn Katan). If you are thinking of a stand mounted monitor that doesn't try to go too deep, rear porting is less of an issue. If floor standing, rear porting is pretty much required to be well away from rear walls.
Still, listen to lots of speakers. A few inches back and forth can make a lot of difference.
Yes front ported will allow you to place them closer to the wall. But don't let that be the deciding vote when making a choice. You can chose a speaker that is rear ported and keep it close to the wall for casual listening. And bring it out when you want to listen more intensely.
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